Agfdhyk

The following code compiles and executes, but nothing is written to the file and I cannot for the life of me figure out why. The file is being created, but the file is empty. I made sure to delete the file each time just in case but that shouldn't make a difference

#include <algorithm>

#include <iostream>

#include <fstream>

#include <string>

#include <iterator>

#include <map>

#include <set>

using namespace std;



int main(){



    set<string> exclusionSet;

    ifstream stopWords("stopwords.txt");

    copy(istream_iterator<string>(stopWords),

            istream_iterator<string>(),

            inserter(exclusionSet, exclusionSet.end()));



    stopWords.close();



    //for_each(exclusionSet.begin(),

//          exclusionSet.end(),

//          (const string& s){cout<<s<<endl;});



    map<string, int> wordMap;

    ifstream words("sample_doc.txt");

    copy_if(istream_iterator<string>(words),

            istream_iterator<string>(),

            inserter(exclusionSet, exclusionSet.end()),

            [=](const string& s){return exclusionSet.find(s)!=exclusionSet.end();});



    ofstream out("frequency.txt");



    for_each(begin(wordMap),

            end(wordMap),

            [&out](const pair<const string, int>& e){ out<<e.first<<" "<<e.second<<endl;});

    out.close();

    return 0;

}

I would suggest the following version of the fixes

int main()

{

    map<string, int> wordMap;



    set<string> exclusionSet;

    ifstream stopWords("stopwords.txt");

    copy(istream_iterator<string>(stopWords), istream_iterator<string>(), inserter(exclusionSet, exclusionSet.end()));

    stopWords.close();



    vector<string> strings;    

    ifstream words("sample_doc.txt");

    copy_if(istream_iterator<string>(words), istream_iterator<string>(), inserter(strings, strings.end()),

        [=](const string& s)

        {

            return exclusionSet.find(s) == exclusionSet.end();

        });

    words.close();



    for(auto &a : strings)

        wordMap[a] = wordMap[a] + 1;



    ofstream out("frequency.txt");



    for_each(begin(wordMap), end(wordMap),

        [&out](const pair<const string, int>& e)

        {

            out << e.first << " " << e.second << endl;

        });



    out.close();

    return 0;

}

Main differences:

1. reading the data from the file "sample_doc" in the vector strings, checking whether they are in exclusionSet (fix yours find_if call)


2. 
   

   forming words frequency statistics with:

   
   
   

   for(auto &a : strings)
   
       wordMap[a] = wordMap[a] + 1;
   
   

   
   

And.... I'd rather replace for_each to range-based for, like this:

for(const auto &e: wordMap)

    out << e.first << " " << e.second << endl;

I don't have much to add on top of @snake_style's answer, but I would like to point out that you can easily drop the complexity/expense of using copy_if to filter the words in sample_doc.txt by using a simple while loop:

#include <algorithm>

#include <iostream>

#include <fstream>

#include <string>

#include <iterator>

#include <map>

#include <set>

using namespace std;



int main(){

    set<string> exclusionSet;

    ifstream stopWords("stopwords.txt");

    copy(istream_iterator<string>(stopWords),

            istream_iterator<string>(),

            inserter(exclusionSet, exclusionSet.end()));



    stopWords.close();



    map<string, int> wordMap;

    ifstream words("sample_doc.txt");

    string s;



    while(words >> s) if (exclusionSet.count(s)==0) ++wordMap[s];



    ofstream out("frequency.txt");



    for_each(begin(wordMap),

            end(wordMap),

            [&out](const pair<const string, int>& e){ out<<e.first<<" "<<e.second<<endl;});

    out.close();

    return 0;

}